It is proposed to test the levels of phospholipase B activity in the small intestines, and the numbers of eosinophils in the bone marrow, of nonsensitized and sensitized rats after challenge with Nippostrongylus brasiliensis. Our tests in mice and rats challenged with Trichinella spiralis showed a close correlation between intestinal inflammation, greatly elevated enzyme levels and increased numbers of eosinophils, all of which were related temporally to worm expulsion. With the view that expulsion of worms from tissues might have a common mechanism, tests in other models (N. brasiliensis-rat, etc.) are proposed.